Dec. 5, 2011 -- On the heels of new revelations about arsenic in grape and apple juice, a new study shows that rice may be a significant source of arsenic in the diets of pregnant women.

Exposure during pregnancy is a concern, experts say, because arsenic is able to cross the placenta and may harm a developing baby.

For the study, researchers measured arsenic levels in the urine of 229 pregnant women in New Hampshire, a state where 40% of people get their water from wells. Well water sometimes has higher levels of arsenic than water from municipal systems, which must meet federal safety standards.

Researchers checked the women’s tap water for arsenic. They also asked the women to write down what food they had eaten in the three days before their urine tests.

Even after accounting for arsenic in drinking water, researchers found that women who had recently eaten rice had slightly higher levels of inorganic arsenic -- the toxic form -- in their urine, compared to women who had not eaten rice.

“Rice, which I think a lot of people would think of as very healthy, may be a real source of exposure to inorganic arsenic, above and beyond drinking-water arsenic,” says Michael S. Bloom, PhD, an assistant professor at the University at Albany in New York.

Bloom is studying the health effects of chronic arsenic exposure. He was not involved in the current research.

For the average person, that means “you may be receiving an additional daily dose through rice. It adds to the cumulative burden of inorganic arsenic exposure,” Bloom says.

Researchers calculated that women who ate just a half cup of cooked rice each day -- the average amount eaten in the study -- would be getting just as much arsenic as if they drank a liter of tap water at EPA’s maximum allowable limit for arsenic.

In a statement, the USA Rice Federation says that comparison is misleading because it fails to recognize that the arsenic in water is all inorganic, the toxic form. Some of the arsenic found in rice is organic, a kind that is believed to be harmless.

Each gram of rice the women ate was associated with a 1% increase in their arsenic levels. A gram of rice is about 48 grains.